Burma's government has said it will open the country to comprehensive international inspection in an effort to demonstrate that it does not have a covert nuclear programme.

The regime said it would sign an agreement with the International Atomic Energy Agency (IAEA) that would, if implemented, mark an important breakthrough in the regime's relations with the rest of the world, and could help dispel longstanding suspicions that it is pursuing a clandestine programme in co-operation with North Korea aimed at building nuclear weapons.

Burma has yet to approach the IAEA formally about the proposal, and hitherto had not been very forthcoming in response to the agency's enquiries about alleged covert work. The IAEA's voluntary additional protocol, which the Burmese government says it will sign, would give the agency's inspectors wide discretion to visit sites of their choosing at short notice, whether the state has declared them to be nuclear-related or not, in order "to assure the absence of undeclared nuclear material and activities".

The Institute for Science and International Security, an independent counter-proliferation watchdog, called this week's Burmese announcement "a remarkable decision".

"This latest move by Burma is extremely positive for its ongoing push for openness about the nuclear issue and for building confidence and transparency with the international community," David Albright and Andrea Stricker wrote on the institute's website.

The nuclear announcement, which was timed to coincide with Barack Obama's landmark visit to Burma this week, are part of a concerted effort by the president, Thein Sein, to break out of international isolation. But US sceptics argue the country should not be rewarded until it has implemented the deal.

"The concern of the international community will not pause until full disclosure of the North Korea-Burma relationship is achieved," the senator Richard Lugar said.

Two years ago, a report on Burma's nuclear aspirations by a former IAEA inspector, Robert Kelley, and commissioned by an opposition group, claimed there was evidence that Burma was carrying out a covert programme. It referred to a secret document from the country's "nuclear battalion", instructing a factory to build a "bomb reactor".

Much of the information came from a Burmese defector, Sai Thein Win, who smuggled hundreds of photographs of the alleged programme when he left the country in 2010. IAEA inspectors were said to be intrigued if not convinced by the Kelley report, and they asked to visit sites mentioned in it. However, the Burmese government did not co-operate.

"Burma may send the additional protocol to parliament and it may be signed. Then it has to be ratified, which many states take months to years to do," Kelley said in a sceptical reaction to the Burmese announcement. "Then Burma will have to submit a declaration of all nuclear materials and nuclear facilities. For countries just stepping up to the plate this process often takes several years."